1. Field of the Invention
The present invention relates to a numerical controller which controls a machine tool. More particularly, the present invention relates to a numerical controller which has the function of controlling the driving of respective axes on the basis of data that is stored in a tabular format.
2. Description of the Related Art
Numerical controllers in which free tool operations that could not be achieved using commands based on conventional blocks are made possible by storing amounts of movement and positions on respective axes in memory beforehand in a tabular format, and controlling the driving of the respective axes on the basis of this data stored in memory (instead of using commands based on blocks of an NC program), so that a shortening of the working time and increased precision of working can be realized, are already universally known.
For example, a technique is known which is devised so that the positions on movable axes for respective times or respective rotational angles are stored in memory as numerical control data, the time or rotational angle is monitored, and numerical control data corresponding to the movable axes is output each time that a stored time or rotational angle is reached (Japanese Patent Application Laid-Open No. S59-177604).
Furthermore, a technique is also known in which a data table that stores command positions on the X axis and Z axis with respect to reference positions is provided, the reference positions are determined by applying an override value to the value of a counter that counts reference pulses, and the X axis and Z axis are synchronously controlled by outputting command positions on the X axis and Z axis stored in the data table on the basis of these reference positions, so that an override is applied even in case where driving control is performed by means of data stored in the data table; moreover, this technique is devised so that command positions can be connected linearly, or with a two- or three-dimensional function or the like, and furthermore auxiliary functions can also be commanded (see Japanese Patent Application Laid-Open No. 2003-303005).
Furthermore, an invention is also known which is devised so that movement commands are output on the basis of a table that stores amounts of movement of the respective axes for each fixed period of time, or movement times for each fixed amount of movement (see Japanese Patent Application Laid-Open No. H6-15547).
In working that is performed in machine tool, there may be cases in which an operation of the same pattern is repeatedly executed in turning finishing cycle working, drill cycle working and the like. If an attempt is made to perform such working in which the same working is repeated using conventional tabular format data, the amount of tabular format data is greatly increased. Since the storage of tabular format data in memory involves the storage of positional data for respective axes in a tabular format using reference times or spindle positions as reference positions, the reference positions differ during each working process even in case where the same working is repeatedly performed, so that the respective axial positions must be stored as data for these reference positions. Consequently, the amount of data is greatly increased, so that the required capacity of the storage means used to store this data is also increased.